As shown in Figure 4-25, routers are designed to support a wide variety of communications protocols: X.25, SDLC, frame relay, TCP/IP, DECnet, IPX, AppleTalk, XNS. It also transports SNA, APPN, and NETBIOS traffic, and functions as a multiport bridge between and among token rings and Ethernets.

Figure 4-25. Typical Router Internetworking Topology

Many routers also provide SDLC to LLC 2 conversion, and a technique called Data Link Switching (DLS), which is used to minimize overhead by allowing the use of SNA, APPN, and NETBIOS over the same physical link, and to transport these protocols between LANs over WANs.


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